[Scenario] Avoid cycle for nasa/MCT-Plugins#31

Detect cycle when answering getAllModifiedObjects
from ActivityComponent by maintaining a
thread-local set of component IDs already
considered by the method call.
[Scenario] Add licenses, organize imports
Merge pull request #63 from VWoeltjen/licenses

[Scenario] Add licenses, organize imports
[Scenario] Find end time in collections

Timeline objects should be able to display
Activities found in Collections in the
Timeline View, nasa/MCT-Plugins#37. Since
Timeline View uses the Timeline component's
end time to determine the displayed time scale,
this means that the Timeline component should
also investigate collections in order to
determine what its end time is.
Merge pull request #65 from VWoeltjen/mctPlugins37

[Scenario] Find end time in collections
Merge pull request #64 from VWoeltjen/mctPlugins31

[Scenario] Avoid cycle for nasa/MCT-Plugins#31
[Scenario] Merge latest from 'nasa/master' into switcher

Complete merge manually to facilitate an
auto-merge by subsequent pull request.